1. Industrial Field of the Invention
The present invention relates to an IC mounting structure to mount an IC chip on an opaque circuit substrate such as a circuit substrate made of epoxy resin and, more specifically, relates to the IC mounting structure which is suitable for positioning, i.e., for alignment of an electrode of the IC chip and a terminal to be arranged on the circuit substrate corresponding thereto with each other. The present invention also relates to a liquid crystal device comprising the IC mounting structure. The present invention further relates to an electronic device comprising the liquid crystal device.
2. Description of the Related Art
Liquid crystal devices have been extensively used in recent years for a visual image display part of portable electronic terminals, electronic notebooks, and other electronic devices. The liquid crystal device is generally formed by attaching a pair of transparent substrates, which are respectively provided with a transparent electrode, to each other with a clearance gap provided therebetween, and filling the liquid crystal in the clearance. A polarizer is further mounted on an outer surface of the transparent substrate as necessary, and a color filter is provided on an inner surface of one transparent substrate as necessary. The light to be supplied to the liquid crystal can be modulated by controlling the orientation of the liquid crystal molecules depending on whether the prescribed voltage is applied or no voltage is applied to the transparent electrodes which are opposite to each other with the liquid crystal provided therebetween. Thereby, the visible information such as characters and numerals is displayed.
Concerning a regular liquid crystal device, in order to control the voltage to be applied to the transparent electrodes opposite to each other at a prescribed amount, the electrode terminal formed on the transparent substrate and the electrode of the IC chip for driving the liquid crystal, e.g., a bump electrode, are positionally adjusted, in other words, aligned, and then, conductive-connected to each other, and thereafter, the prescribed voltage is applied to the transparent electrodes in accordance with the instruction from the IC chip. Various kinds of methods to connect the IC chip for driving the liquid crystal to the transparent substrate have been conventionally known. For example, as seen in the liquid crystal device of the so-called COG (Chip On Glass) system, there is an IC mounting structure, where the IC chip is directly mounted on the transparent substrate comprising the liquid crystal panel is known.
According to the IC mounting structure, the IC chip can be observed through the substrate using a camera because the substrate on which the IC chip is mounted is transparent. Accordingly, the alignment of the substrate and IC chip is performed by a simple work. When the IC chip is directly mounted on the transparent substrate, the circuit constitution accompanied by the IC chip is required to be formed on the transparent substrate by ITO (Indium Tin Oxide), etc. In such case, however, no complicated circuit constitution can be formed on the transparent substrate.
On the other hand, when the circuit substrate is formed using an opaque material such as glass epoxy resin, a complicated circuit can be formed. For example, a circuit can be formed on both faces of the circuit substrate and connected to each other using a through hole. When the IC chip is mounted on such an opaque circuit substrate, for example as indicated in FIG. 8, an IC chip 53 for driving the liquid crystal is adhered to an opaque circuit substrate 51 using an adhesive such as ACF (Anisotropic Conductive Film) 52. Further, when the formed circuit substrate unit is mounted on the liquid crystal panel of the liquid crystal device, a bottom side of the opaque circuit substrate 51 is adhered to the transparent substrate of the liquid crystal panel.
As indicated in FIG. 8, when the IC chip 53 is mounted on the opaque circuit substrate 51, an alignment mark 54K is formed at the prescribed position of the circuit substrate 51 in the conventional practice, while an alignment mark 54I is formed at the prescribed position of an active side 53a of the IC chip 53, and the IC chip 53 is adhered to the circuit substrate 51 in a condition where both alignment marks 54K and 54I are adjusted to each other to be at the same position.
An electrode, for example, a bump electrode 55 is formed on the active side 53a of the IC chip 53. An electrode terminal 65 is formed on a surface of the circuit substrate 51. Wiring is formed depending on the situation between bump electrodes 55 and between electrode terminals 65, which is not shown in the figure. The alignment marks 54K and 54I are used for positioning the electrodes 55 and the electrode terminals 65, i.e., for alignment with each other.
To positionally align both alignment marks 54K and 54I with each other, the following process is performed in the conventional practice. That is, a prism 56 to guide the light to the camera or the camera itself (not shown in the figure) is inserted between the circuit substrate c1 and the IC chip 53, the alignment mark 54I on the IC chip and the alignment mark 54K on the circuit substrate are successively photographed using the prism 56 or the like, the prism 56 is pulled out from between the circuit substrate 51 and the IC chip 53, the position of the circuit substrate 51 and the IC chip 53 is adjusted based on the photographed image by the camera, and then, the circuit substrate 51 and the IC chip 53 are adhered to each other.
However, in the conventional IC mounting structure, the prism 56 or the camera itself (not shown in the figure) must be inserted or pulled out between the circuit substrate 51 and the IC chip 53 to align the circuit substrate 51 with the IC chip 53, and the photographing view of the inserted prism 56 or the camera must be changed by turning between the circuit substrate 51 and the IC chip 53, and as a result, it takes a very long time to align the circuit substrate 51 with the IC chip 53, presenting a problem in that the productivity is worsened.
The present invention is performed in light of the above-mentioned problem in the conventional IC mounting structure, and the object of the present invention is to perform the work to mount the IC chip on the opaque circuit substrate with an extremely simple and quick process.